Magnetic tape has not been around for many decades. As the magnetic oxide crystals continue to grow smaller and the number of bits of information stored on the tape grow larger, it becomes more demanding that the surface of the tape is as nearly perfectly "clean" as possible to prevent dropping bits of information because of poor tape-to-head contact. An excellent discussion of the magnetic tape, the inclusion of the high density of bits and the necessity for cleaning is given in U.S. Pat. No. 3,587,128. That patent reports the manufacture of the tape by the tedious and exacting process of growing magnetic oxide crystals and applying them to a sheet of base material such as acetate or Mylar polyester film approximately 0.001 inch thick in a plastic vehicle form of coating material and thereafter cutting the tape to the desired length and width. Therein is also described the high density of information bits for current computer users with multiple head arrangements and the "signal drop out", an unwanted condition causing the read-out head to drop bits of information because of high spots, or debris, on the surface of the tape that prevents good tape-to-head contact. That patent goes on to describe several cleaning methods and apparatus such as disclosed in U.S. Pat. No. 3,035,295, employing a metal scraper. That patent goes on to point out the disadvantages of the metal scraper blade in leaving bits of metal and forming an uneven cutting edge that scrapes, scratches, or otherwise damages the tape. The solution as delineated in that patent is to use a hard monocrystalline material such as sapphire or ruby that is harder than the oxide coating on the tape and which can be formed into a uniform cutting edge to achieve superior results.
Illustrative of other tape cleaning apparatus are those pieces of apparatus described in the following U.S. Pat. Nos.: 3,266,196 describes a tape cleaner employing a gear reducer for driving the tape cleaning head. 3,475,782 describes a magnetic tape cleaner in which slight distortion of the tape is effected by two rollers 43 on either side of the cleaning head 19. 3,587,128 has already been described hereinbefore and discloses the use of a hard monocrystalline material in the scraper blade means for scraping the front surface of the tape. 3,701,178 describes a cassette tape cleaner in which a plurality of scraping blades project into standard openings in the cassette when the cassette is inserted in the apparatus and employing a blast of air to remove scrapings away from the blades and the tape. 3,757,374 describes a magnetic tape cleaner in which the tape contact the edge of a blade and then onto a take-up reel, the blade having a plurality of cutting edges and lengths at least twice the width of the tape to be cleaned. That apparatus then rotates the blade holding member so that the edge of the blade is used in succession and when all exposed edges of the blades have been used to clean the tape, the blade is removed from the holder and repositioned with the unexposed portion ready for use, thereby doubling the useful life of a blade.
Looking at another aspect of the invention, there is published in the IBM Technical Disclosure Bulletin, volume 1, number 6, April 1959, a method of cleaning magnetic tape in which it is run through a solution having ultrasonic agitation, the solution being selected to be 100 percent (%) volatile so as to leave no residue on the tape.
From the foregoing, it can be seen that the prior art has provided a variety of means of cleaning magnetic tape to avoid scratching, leaving metallic particles thereon, leaving other undesirable debris and attempting to prevent unwanted "drop out" of bits of information from faulty tape-to-head contact when subsequently used; yet, the prior art approaches have not been totally satisfactory, probably because embedded debris was not adequately removed by the blades nor by the ultrasonic vibration in a solution.